Mercer Island Lake Line Permitting

Surveying nearshore habitat and
documenting existing conditions.

Shoreline improvements create challenges for
lake line replacement.

Existing lake line crossing sockeye spawning
habitat.

Confluence Environmental Company staff provided regulatory compliance support, environmental review, permitting, and strategic input integral for the construction of a 2.5-mile, in-lake sewer line segment along the Lake Washington shoreline. The project was particularly challenging because of the sensitive shoreline resources including Endangered Species Act (ESA)-listed species, the technical challenges of maintaining reliable sewer service to shoreline residents during construction, and the timing constraints for in-water work in Lake Washington.

Approach

Confluence’s Chris Cziesla led the effort to complete a shoreline fish and wildlife habitat inventory and prepare all environmental permit documents, including a full SEPA environmental impact statement, Shoreline Habitat Inventory, ESA biological assessment, Clean Water Act Section 404(b)(1) Analysis, and JARPA submittal (for Corps Section 404 and 10, Hydraulic Project Approval, 401 Water Quality Certification, Coastal Zone Management consistency, Shoreline permit). Mitigation and shoreline restoration, such as riparian improvements, bulkhead removal, invasive species removal, and substrate augmentation were also included as part of the project. Confluence’s technically sound analyses, timely response, and excellent working relationships with the client, regulators, and contractors paved the way for a dynamic team able to respond to changing project concerns and constraints. Strong relationships with the following regulatory agencies were critical in allowing the city and their construction contractor flexibility in their construction approach: